<!DOCTYPE html>
<html>
<head>
  <title>下拉菜单</title>
  <style>
    .dropdown {
      position: relative;
      display: inline-block;
    }

    .dropdown-content {
      display: none;
      position: absolute;
      background-color: #f9f9f9;
      min-width: 120px;
      box-shadow: 0 8px 16px 0 rgba(0,0,0,0.2);
      z-index: 1;
    }

    .dropdown:hover .dropdown-content {
      display: block;
    }

    .dropdown-content a {
      color: black;
      padding: 12px 16px;
      text-decoration: none;
      display: block;
    }

    .dropdown-content a:hover {
      background-color: #f1f1f1;
    }
  </style>
</head>
<body>

<div class="dropdown">
    <span>微博</span>
    <span>微博</span>
  <span>微博</span>
  <div class="dropdown-content">
    <a href="#">私信</a>
    <a href="#">评论</a>
    <div class="dropdown">
      <span>子菜单</span>
      <div class="dropdown-content">
        <a href="#">@我</a>
        <a href="#">私信</a>
      </div>
    </div>
  </div>
</div>

</body>
</html>
